Do not publish public keys extractable from ID

Initial implementation for ipfs#3896

The function `peer.ExtractPublicKey()` is part of PR libp2p/go-libp2p-peer#14

cc @whyrusleeping

namesys/publisher.go

@@ -150,21 +150,36 @@ func PutRecordToRouting(ctx context.Context, k ci.PrivKey, value path.Path, seqn
 		entry.Ttl = proto.Uint64(uint64(ttl.Nanoseconds()))
 	}
 
-	errs := make(chan error, 2)
+	var errorChanSize int
+	var errorChan chan error
 
-	go func() {
-		errs <- PublishEntry(ctx, r, ipnskey, entry)
-	}()
+	// Attempt to extract the public key from the ID
+	var extractedPublicKey = peer.ExtractPublicKey()
+
+	if extractedPublicKey == nil {
+		errorChanSize = 2 // IPNS and public key
+	} else {
+		errorChanSize = 1 // IPNS only
+	}
+
+	errorChan = make(chan error, errorChanSize)
 
 	go func() {
-		errs <- PublishPublicKey(ctx, r, namekey, k.GetPublic())
+		errorChan <- PublishEntry(ctx, r, ipnskey, entry)
 	}()
 
-	if err := waitOnErrChan(ctx, errs); err != nil {
-		return err
+	// Publish the public key if a public key cannot be extracted from the ID
+	if extractedPublicKey == nil {
+		go func() {
+			errorChan <- PublishPublicKey(ctx, r, namekey, k.GetPublic())
+		}()
+
+		if err := waitOnErrChan(ctx, errorChan); err != nil {
+			return err
+		}
 	}
 
-	return waitOnErrChan(ctx, errs)
+	return waitOnErrChan(ctx, errorChan)
 }
 
 func waitOnErrChan(ctx context.Context, errs chan error) error {